FreeBSD Manual Pages
std::nullptr_t(3) C++ Standard Libary std::nullptr_t(3) NAME std::nullptr_t - std::nullptr_t Synopsis Defined in header <cstddef> typedef decltype(nullptr) nullptr_t; (since C++11) std::nullptr_t is the type of the null pointer literal, nullptr. It is a distinct type that is not itself a pointer type or a pointer to member type. Its values are null pointer constants (see NULL), and may be implicitly converted to any pointer and pointer to member type. sizeof(std::nullptr_t) is equal to sizeof(void *). Notes nullptr_t is available in the global namespace when <stddef.h> is included, even if it is not a part of C. Example If two or more overloads accept different pointer types, an overload for std::nullptr_t is necessary to accept a null pointer argument. // Run this code #include <cstddef> #include <iostream> void f(int*) { std::cout << "Pointer to integer overload\n"; } void f(double*) { std::cout << "Pointer to double overload\n"; } void f(std::nullptr_t) { std::cout << "null pointer overload\n"; } int main() { int* pi {}; double* pd {}; f(pi); f(pd); f(nullptr); // would be ambiguous without void f(nullptr_t) // f(0); // ambiguous call: all three functions are candidates // f(NULL); // ambiguous if NULL is an integral null pointer con- stant // (as is the case in most implementations) } Output: Pointer to integer overload Pointer to double overload null pointer overload See also nullptr(C++11) the pointer literal which specifies a null pointer value NULL implementation-defined null pointer constant (macro constant) is_null_pointer checks if a type is std::nullptr_t (C++14) (class template) http://cppreference.com 2022.07.31 std::nullptr_t(3)
NAME | Synopsis | Notes | Example | Output: | See also
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::nullptr_t&sektion=3&manpath=FreeBSD+Ports+15.0>